The decay of wood and other cellulosic materials by fungi causes significant economic loss. Until recently, the most widely used wood preservative has been chromated copper arsenate (CCA). However, concerns have been raised about the environmental impact of arsenic and chromium used in CCA-treated lumber. To address these issues, arsenic- and chromium-free wood preservatives are sought.
Wood preservation formulations containing copper-chelating molecules are known in the art. One such preservative system is based on a copper complex, Cu-HDO, which contains a bidentate ligand, N-nitrosylated cyclohexyl-hydroxylamine (DE U.S. Pat. No. 3,835,370). Another alternative wood preservative is ACQ, an Ammoniacal Copper Quaternary compound (U.S. Pat. No. 4,929,454).
Many metal-chelating functionalities are known, causing a central metal ion to be attached by coordination bond to two or more nonmetal atoms (ligands) in the same molecule. Heterocyclic rings are formed with the central (metal) atom as part of each ring. Polyhydroxamic acids are known and have been shown to complex with copper. Amidoxime or hydroxamic acids of cyanoethylated cellulose are known as complexation agents for metal ions, including copper (Altas H. Basta, International Journal of Polymeric Materials, 42, 1-26 (1998)).
A challenge is obtaining adequate penetration of wood by preservative agents, which typically occurs during imbibing of aqueous wood preservatives. Penetration of an effective amount of preservative agent to adequately protect wood from decay is needed. The acidic CCA wood preservative provides complete and thorough penetration of the preservative agents into wood. However, wood preservatives developed to replace CCA are typically basic systems such as ammoniacal copper quaternary(ACQ). Generally, in basic wood preservative solutions, the typically used copper ion preservative agent penetrates less well. This reduced penetration results in a sharply decreasing gradient of preservative agent from the surface to the center of a treated article. To establish an effective concentration of preservative agent deep in the wood, high concentrations of preservative agents are needed in the wood preservative solution.
There thus remains a need for wood preservative compositions which are relatively easy to handle and provide improved penetration of the wood preservative agent.